Service names and port numbers are used to distinguish between different
services that run over transport protocols such as TCP, UDP, DCCP, and
SCTP.
Service names are assigned on a first-come, first-served process, as
documented in [RFC6335].
Port numbers are assigned in various ways, based on three ranges: System
Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private
Ports (49152-65535); the difference uses of these ranges is described in
[RFC6335]. According to Section 8.1.2 of [RFC6335], System Ports are
assigned by the "IETF Review" or "IESG Approval" procedures described in
[RFC8126]. User Ports are assigned by IANA using the "IETF Review" process,
the "IESG Approval" process, or the "Expert Review" process, as per
[RFC6335]. Dynamic Ports are not assigned.
The registration procedures for service names and port numbers are
described in [RFC6335].
Assigned ports both System and User ports SHOULD NOT be used without
or prior to IANA registration.
************************************************************************
* PLEASE NOTE THE FOLLOWING: *
* *
* ASSIGNMENT OF A PORT NUMBER DOES NOT IN ANY WAY IMPLY AN *
* ENDORSEMENT OF AN APPLICATION OR PRODUCT, AND THE FACT THAT NETWORK *
* TRAFFIC IS FLOWING TO OR FROM A REGISTERED PORT DOES NOT MEAN THAT *
* IT IS "GOOD" TRAFFIC, NOR THAT IT NECESSARILY CORRESPONDS TO THE *
* ASSIGNED SERVICE. FIREWALL AND SYSTEM ADMINISTRATORS SHOULD *
* CHOOSE HOW TO CONFIGURE THEIR SYSTEMS BASED ON THEIR KNOWLEDGE OF *
* THE TRAFFIC IN QUESTION, NOT WHETHER THERE IS A PORT NUMBER *
* REGISTERED OR NOT. *
************************************************************************

This is a duplicate of the "http" service and should not be used for discovery purposes.
u=<username> p=<password> path=<path to document>
(see txtrecords.html#http)
Known Subtypes: _printer
NOTE: The meaning of this service type, though called just "http", actually
denotes something more precise than just "any data transported using HTTP".
The DNS-SD service type "http" should only be used to advertise content that:
* is served over HTTP,
* can be displayed by "typical" web browser client software, and
* is intented primarily to be viewed by a human user.
Of course, the definition of "typical web browser" is subjective, and may
change over time, but for practical purposes the DNS-SD service type "http"
can be understood as meaning "human-readable HTML content served over HTTP".
In some cases other widely-supported content types may also be appropriate,
such as plain text over HTTP, or JPEG image over HTTP.
Content types not intented primarily for viewing by a human user, or not
widely-supported in web browsing clients, should not be advertised as
DNS-SD service type "http", even if they do happen to be transported over HTTP.
Such types should be advertised as their own logical service type with their
own DNS-SD service type, for example, XUL (XML User Interface Language)
transported over HTTP is advertised explicitly as DNS-SD service type "xul-http".

This is a duplicate of the "http" service and should not be used for discovery purposes.
u=<username> p=<password> path=<path to document>
(see txtrecords.html#http)
Known Subtypes: _printer
NOTE: The meaning of this service type, though called just "http", actually
denotes something more precise than just "any data transported using HTTP".
The DNS-SD service type "http" should only be used to advertise content that:
* is served over HTTP,
* can be displayed by "typical" web browser client software, and
* is intented primarily to be viewed by a human user.
Of course, the definition of "typical web browser" is subjective, and may
change over time, but for practical purposes the DNS-SD service type "http"
can be understood as meaning "human-readable HTML content served over HTTP".
In some cases other widely-supported content types may also be appropriate,
such as plain text over HTTP, or JPEG image over HTTP.
Content types not intented primarily for viewing by a human user, or not
widely-supported in web browsing clients, should not be advertised as
DNS-SD service type "http", even if they do happen to be transported over HTTP.
Such types should be advertised as their own logical service type with their
own DNS-SD service type, for example, XUL (XML User Interface Language)
transported over HTTP is advertised explicitly as DNS-SD service type "xul-http".